INTRODUCTION: Although common hematological abnormalities (CHA) such as anemia, macrocytosis, and platelet dysfunction are often present in patients with schizophrenia, empirical data are limited. Thus far, such deviations have been mentioned either in reports or in a series of clinical cases. AIM: To study the incidence of CHA in patients with schizophrenia. MATERIALS AND METHODS: This study involved 791 patients with schizophrenia [including those who did not receive medical drugs (n = 115) and patients with chronic schizophrenia (n = 376)] and 504 healthy volunteers. From each participant, blood samples were taken and analyzed for CHA using an automatic Coulter counter. In the three groups, 2 tests and analysis of variance (ANOVA) were conducted to compare the variables. RESULTS: The incidence of macrocytosis was nearly the same in the schizophrenia group (patients not receiving medications, 10.5%; patients with chronic schizophrenia, 10.6%) and was significantly higher than that in the control group (4.2%). The platelet count was considerably higher in the chronic schizophrenia group ([282.5 87.9] 103/L) than in the group not receiving medical drugs ([277.0 92.8] 103/L) and control group ([249.6 85.2] 103/L), whereas the differences in the concentration of hemoglobin and leukocytes in the blood were insignificant. CONCLUSION: Patients with schizophrenia have a higher proportion of macrocytosis in combination with increased platelet count, which shows that the underlying diseases should be diagnosed and treated as early as possible. Moreover, prospective studies with a larger sample size are necessary to determine the etiology of these conditions in patients with schizophrenia.